1. Field of the Invention
The present invention relates to motors and more particularly, to a compact and inexpensive motor that dissipates heat quickly during operation.
2. Description of the Related Art
FIGS. 1 and 2 show a motor according to the prior art. According to this design, the motor 10 is comprised of an outer shell 11, a stator 12, a rotor 13, a front cover 14, and a back cover 15. The outer shell 11 has a plurality of radiation ribs 111 spaced around the periphery, and a plurality of screw holes 110 symmetrically formed in the two end walls. The stator 12 is fixedly mounted inside the outer shell 11, comprising a plurality of silicon steel sheet members 120 arranged in a stack, an electrically insulative winding holder 122 axially mounted in the stack of silicon steel sheet members 120, and an enameled wire 121 wound on the electrically insulative winding holder 122 to form windings around the inner diameter of the stack of silicon steel sheet members 120. The front and back covers 14 and 15 are respectively covered on the two distal ends of the outer shell 11, each having a center axle bearing 141, an annular locating flange 142 protruded from the inner wall around the center axle bearing 141 and fitted into the outer shell 11, and a plurality of mounting screw holes 140 respectively fastened to the screw holes 110 of the outer shell 11 with a respective screw. The rotor 13 is supported in the center axle bearings 141 of the covers 14 and 15 and suspending inside the outer shell 11 within the stator 12.
This design of motor 10 is still not satisfactory in function. The use of the outer shell 11 greatly increases the dimensions of the motor 10 and complicates the fabrication of the motor 10, resulting in a high manufacturing cost. Further, because the stator 12 is mounted inside the outer shell 11, heat produced by the silicon steel sheet members 120 during operation of the motor 10 is dissipated into the outside air through the radiation ribs 111 of the outer shell 11, i.e., the silicon steel sheet members 120 cannot receive cooling air to dissipate heat efficiently. Because of poor heat dissipation effect, this design of motor 10 is not durable in use.